I. Field of Invention
The invention generally relates to secure communication systems and more particularly, to access key management for multimedia broadcasting service in a mobile environment.
II. Description of the Related Art
Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), or other modulation techniques.
A system may be designed to support one or more standards such as the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard); the “Global System for Mobile” (GSM) communication standard based on TDMA; the “Universal Mobile Telecommunications Service” (UMTS) standard which is a third generation wireless service based on GSM communication standard; the General Packet Radio System (GPRS) communication standard which is an evolutionary step from GSM toward UMTS; the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) which is embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214, 3G TS 25.302 (the W-CDMA standard); the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) which is embodied in “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems” (the IS-2000 standard). Each standard defines the processing of data for wireless communication between an infrastructure element, such as a base station, and a user end device, such as a mobile device.
Increasing demand for wireless data transmission and the expansion of services available via wireless communication technology have led to the development of specific data services. In one embodiment, a system may be configured to support multimedia broadcasting services (hereinafter “broadcast service”). Similar to television and/or radio broadcasting, broadcast service may be used for wireless transmission of multimedia content stream from a content provider to user end devices. Here, a content stream can be considered as equivalent to a television channel or radio station. Examples of multimedia content streams include audio and/or video data such as movies, sports events, news and various other programs and/or files. Typically, a service provider indicates the availability of such broadcast service to users. Users desiring broadcast service may receive broadcast service related parameters in overhead messages transmitted by infrastructure elements. When a user desires to receive certain content stream, the user end device reads the overhead messages and learns the appropriate configurations. The user end device then tunes to the channel or frequency containing the content stream, and receives broadcast service.
There are several possible subscription/revenue models for broadcast service, including free access, controlled access, and partially controlled access. For free access, no subscription is needed by the users to receive the service. Content is broadcasted without encryption such that user end devices of interested users can receive and view the content. The revenue for the service provider can be generated through advertisements that may also be transmitted in the broadcast channel. For example, upcoming movie-clips can be transmitted for which the studios will pay the service provider.
In controlled access, users are required to subscribe and become authorized to receive the broadcast service by paying a fee. This controlled access can be achieved by encrypting the broadcast service transmission or content with cryptographic access keys such that only subscribed users can decrypt and view the content. Here, the encryption of the broadcast content may be based on symmetric or asymmetric cryptosystems. In symmetric cryptosystems, the same keys are used for encryption/decryption and in asymmetric cryptosystems, different keys are used for encryption/decryption.
Cryptography is well known to those skilled in art and will not be further described in detail. A hybrid access scheme or partial controlled access provides broadcast service as a subscription-based service that is encrypted with intermittent unencrypted advertisement transmissions. These advertisements may be intended to encourage subscriptions to the encrypted broadcast service.
For controlled or partially controlled broadcast service, a problem exists in the secure provision of the access key from a content provider to one or more recipients. Therefore, there is a need for a secure way to provision an access key to end user devices. More particularly, the provisioning of the access key needs to conform with existing standards and corresponding infrastructures as well as evolving standards and corresponding infrastructures.